Isomers of poly(9-fluorenone), such as 2,7-poly(9-fluorenone), may be employed in bi/multilayer light-emitting diodes (LED) operated with Mg as a cathode. Uckert, F. et. al., Advanced Materials, Vol. 12, No. 12, p.p. 905–908 (2000). However, poly(9-fluorenone) has proven difficult to prepare, in particular, 9-fluorenone does not appear to have been electrolytically polymerized to date. Zecchin, S., et al., Journal of Electroanalytical Chemistry, Vol. 215, p.p. 377–383 (1986).
Currently, there are two main methods for preparing poly(9-fluorenone), and in particular, 2,7-poly(9-fluorenone). One method uses five separate and distinct steps, starting from malonic ester. The malonic ester is treated to produce 2,2-dioctylmalonic ester and in a separate step subsequently reduced with lithium aluminum hydride to provide a diol compound, 2,2-dioctyl-1,3-propanediol. The diol compound is then combined with 2,7-dibromo(9-fluorenone) which must be produced from fluorene in two separate steps. The result of the combination of the diol with the 2,7-dibromo(9-fluorenone), under appropriate conditions, is 2,7-dibromo-spiro(4′,4′-dioctyl-2′,6′-dioxocyclohexane-1′,9-fluorene). The 2,7-dibromo-spiro(4′,4′-dioctyl-2′,6′-dioxocyclohexane-1′,9-fluorene) is polymerized with a nickel catalyst to provide 2,7-poly(spiro(4′,4′-dioctyl-2′,6′-dioxocyclohexane-1′, 9-fluorene)). The 2,7-poly(spiro(4′,4′-dioctyl-2′,6′-dioxocyclohexane-1′,9-fluorene)) is treated with dichloroacetic acid to give the final product, 2,7-poly(9-fluorenone). Uckert, F., et al., Macromolecules, Vol. 32, No. 14, p.p. 4519–4524 (1999).
In a second method for preparing poly(9-fluorenone), 2,7-dibromo-9-fluorenone, obtained by a two-step process from fluorene, is converted to Ni(PPh3)2(2-bromo-7-fluorenonyl)Br, which is then reduced electrochemically to give 2,7-poly(9-fluorenone). Zecchin, S., et al., Journal of Electroanalytical Chemistry, Vol. 215, p.p. 377–383 (1986).
Each method requires several separate steps and both have proven to be complicated and troublesome, involving the use of many potentially hazardous chemicals. Further, the methods have generally resulted in low polymer yields and high levels of impurities or byproducts.
Recently, Zecchin et al. alleged that 2,7-poly(9-fluorenone) films could be obtained from 2,7-poly(fluorene) films via oxidation with electrochemically generated superoxide. Zecchin, S., et al., Journal of Electroanalytical Chemistry, Vol. 215, p.p. 377–383 (1986). The report, however, provided no analysis of the film material to support the findings and Uckert et al. (Macromolecules, Vol. 32, No. 14, p.p. 4519–4524 (1999)) has disputed that the polymer obtained was in fact 2,7-poly(9-fluorenone), based on inconsistencies within Uckert's data. Therefore, it is unclear if the Zecchin described superoxide method has utility for preparing poly(9-fluorenone).
As such, the methods for preparing poly(9-fluorenone) have proven to be of limited value. Accordingly there is a need for a simple and cost-effective method for producing poly(9-fluorenone) as well as other polymers having cyclopentanone structures. Against this backdrop the present invention has been developed.